1. Field of the Invention
Embodiments of the invention generally relate to an integrated processing system containing multiple processing stations and robots that are capable of processing multiple substrates in parallel.
2. Description of the Related Art
The process of forming electronic devices is commonly done in a multi-chamber processing system (e.g., a cluster tool) that has the capability to sequentially process substrates, (e.g., semiconductor wafers) in a controlled processing environment. Typical cluster tools used to perform semiconductor cleaning processes, commonly described as a wet/clean tool, will include a mainframe that houses at least one substrate transfer robot which transports substrates between a pod/cassette mounting device and multiple processing chambers that are connected to the mainframe. Cluster tools are often used so that substrates can be processed in a repeatable way in a controlled processing environment. A controlled processing environment has many benefits which include minimizing contamination of the substrate surfaces during transfer and during completion of the various substrate processing steps. Processing in a controlled environment thus reduces the number of generated defects and improves device yield.
The effectiveness of a substrate fabrication process is often measured by two related and important factors, which are device yield and the cost of ownership (CoO). These factors are important since they directly affect the cost to produce an electronic device and thus a device manufacturer's competitiveness in the market place. The CoO, while affected by a number of factors, is greatly affected by the system and chamber throughput, or simply the number of substrates per hour processed using a desired processing sequence. A process sequence is generally defined as the sequence of device fabrication steps, or process recipe steps, completed in one or more processing chambers in the cluster tool. A process sequence may generally contain various substrate (or wafer) electronic device fabrication processing steps. In an effort to reduce CoO, electronic device manufacturers often spend a large amount of time trying to optimize the process sequence and chamber processing time to achieve the greatest substrate throughput possible given the cluster tool architecture limitations and the chamber processing times.
Other important factors in the CoO calculation are the system reliability and system uptime. These factors are very important to a cluster tool's profitability and/or usefulness, since the longer the system is unable to process substrates the more money is lost by the user due to the lost opportunity to process substrates in the cluster tool. Therefore, cluster tool users and manufacturers spend a large amount of time trying to develop reliable processes, reliable hardware, reliable transferring methods and reliable systems that have increased uptime.
Extraordinarily high levels of cleanliness are generally required during the fabrication of semiconductor substrates. During the fabrication of semiconductor substrates, multiple cleaning steps are typically required to remove impurities from the surfaces of the substrates before subsequent processing. The cleaning of a substrate, known as surface preparation, has for years been performed by collecting multiple substrates into a batch and subjecting the batch to a sequence of chemical and rinse steps and eventually to a final drying step. A typical surface preparation procedure may include etch, clean, rinse and dry steps. During a typical cleaning step, the substrates are exposed to a cleaning solution that may include water, ammonia or hydrochloric acid, and hydrogen peroxide. After cleaning, the substrates are rinsed using ultra-pure water and then dried using one of several known drying processes.
Moreover, the push in the industry to shrink the size of semiconductor devices to improve device processing speed and reduce the generation of heat by the device, has reduced the industry's tolerance for process variability. To minimize process variability an important factor in semiconductor fabrication processes is the issue of assuring that every substrate run through a cluster tool sees the same processing conditions or receives the highest quality deposition or cleaning process steps. Conventional batch cleaning processes often do not provide results that are repeatable and uniform for each substrate positioned within the batch or from batch to batch.
In some cases, various semiconductor processes are advantageously performed using a substrate in a vertical orientation, wherein the typical processing surface(s) of the substrate face a horizontal direction. Such processes generally include cleaning processes (e.g., Marangoni drying), where insertion and removal of the substrate are critical to the performance of the process, or where the footprint of the processing apparatus is minimized by processing the substrate in a vertical orientation. However, batches of substrates are typically transferred and positioned in an input device in a cluster tool, such as a substrate cassette and/or FOUPs in a horizontal orientation. Transferring and supporting batches of substrates in a horizontal orientation is advantageous, because of the likelihood of generating particles due to the tipping and/or “rattling” of the substrates in the cassette due to the inherent instability of a semiconductor substrate that is positioned in a vertical orientation. Therefore, to transfer, orient and position a substrate from a horizontal to a vertical orientation requires the use of one or more substrate tilting device. Conventional processing systems generally require at least one or more devices positioned within each processing chamber or in a position near the processing chamber to rotate the substrate in a vertical orientation so that it can be processed vertically. In some cases multiple substrate tilting devices can be used to rotate the substrate into a vertical orientation to avoid being a bottleneck to the process sequence. Having multiple substrate tilting devices can greatly affect the reliability of the cluster tool, since the overall system reliability is proportional to the product of the reliability of each component in the system. Thus adding multiple chambers that can tilt or rotate a substrate to a vertical orientation degrades the reliability of the whole cluster tool.
Also, the process of rapidly transferring and positioning a substrate in a cluster tool generally requires a robot to grip the substrate so that the substrate will not slide on the robot blade while robot is accelerated and decelerated during the transferring process. Sliding on the robot blade will generate particles and/or cause the substrate to become chipped, which greatly affects device yield and CoO performance of the cluster tool.
Therefore, there is a need for a system, a method and an apparatus that can transfer and receive a substrate in a horizontal and vertical orientation, provide a reliable transferring process. There is also a need for a cluster tool that can meet the required device performance goals, has a high substrate throughput, and thus reduces the process sequence CoO.